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I live close to an AM transmitter broadcasting in the kW of power. My RTL SDR dongle gets very overloaded. Using 2 AM broadcast filters, I have mostly managed to stop the overloading, at least from the main frequency.

However, generally on all bands, especially on HF, there is just a lot of noise. I assume this large amount of noise is due to the nearby AM transmitter.

My question is: given that I use a random long wire antenna going into my 9:1 "balun", is there a way to reduce noise? Would a good ground rod help?

I'm quite new to antenna design, and I'm unsure that when I do different random things (e.g. increase/decrese length or move it) to my long wire, when the noise reduces, I'm not sure if I've just attenuated my overall signal, or somehow managed to reduce the noise.

I don't understand if there is a distinction between noise and wanted signals when it comes to antenna design/placement.

Thanks

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Their are two types of sources that noise can come from.

  1. Environmental > What Nature doles out.
  2. interference from devices and electronics.

Electronics are big culprits, I had to turn off my computer monitor just to listen to commercial stations.

What I would do is first make sure that no other electronics are near the equipment. first by turning off everything, then tune in and then turn things on one by one, their you can pin point where the noise is coming from, if you found the culprit then relocate the item.

Then if that is not the problem check shielding on the cable to your radio antenna.

if anything else above does not remedy then I suspect something inside your radio equipment is emitting where it should not be.

for the interest i did a little digging and found this:

https://www.rtl-sdr.com/tip-effect-of-power-sources-on-the-ham-it-up-upconverter/

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  • $\begingroup$ My antenna is a long wire stretched out the window, going into an RTL 9:1 balun, then going into 2 AM filters, a ham it up converter and finally to RTL-SDR, going into a raspberry pi. I actually don't have any antenna feeder as the whole chain is barrel connected (well, there is a 3 inch long pigtail from the converter to the SDR). This setup is in a back bedroom with nothing else switch on. Of course, there could be something else coming from the house. If it's the strong AM transmitters nearby, I guess I'm out of luck? $\endgroup$
    – user14615
    Apr 9, 2019 at 15:25
  • $\begingroup$ @user14615 is your RX antenna lower then the TX antenna (sorry i got to use abbreviations $\endgroup$
    – Ben Madison KO4UXC
    Apr 9, 2019 at 15:35
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    $\begingroup$ @user14615 strong AM transmitter would not cause what you are seeing, unless it is overloading your receiver. Electronics such as a cheap LED light, a WRT45g router, or a cheap wall wart power supply (...or any number of other things...) can easily cause this, even if in a far part of the house or in use by a neighbor. Diagnosing and fixing noise is Not Easy. $\endgroup$
    – Chris K8NVH
    Apr 9, 2019 at 15:39
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    $\begingroup$ @user14615 Can you try to post a sound sample, I can guess at what is going on without having an hearing of the problem. $\endgroup$
    – Ben Madison KO4UXC
    Apr 9, 2019 at 16:13
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    $\begingroup$ Thank you for this advice. I did turn off my main circuit breaker and did indeed find a device that was causing some noise in and around the 80m band. I'll see if I can get a sound sample of the remaining noise, but based on this experience, I think it's just general electronics from my neighbours which can't really be helped. $\endgroup$
    – user14615
    Apr 11, 2019 at 15:27
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First try isolating your noise sources. If you have a portable antenna and battery power system, move away from your house and all other structures with electric power, but the same distance from the AM station(s), and check the noise levels. Then travel away from the AM station. If it's in your house, kill circuit breakers room-by-room to isolate powered interfering sources (sometimes LED lighting systems, or network routers, etc.).

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